1. Technical Field
The present invention relates to a process for the preparation of poly-α-glutamic acid and derivatives thereof, and compounds therefrom.
2. Description of the Related Art
Poly-α-glutamic acid of formula (I)
is currently used as drug delivery system, for example for the preparation of conjugates with a wide variety of drugs containing a primary or secondary amino group as well as primary, secondary or tertiary hydroxy groups. The conjugation can occur directly or through a suitable linker, for example an amino acid or a hydroxyacid. See, for example, EP0932399, Advanced Drug Delivery Reviews, Volume 54, Issue 5, 2002, Pages 695-713 and Journal of Controlled Release, Volume 74, Issues 1-3, 2001, Pages 243-247.
Poly-α-glutamic acid can be synthesized by polymerization of suitably protected glutamic acid. U.S. Pat. No. 3,635,909 discloses, inter alia, the polymerization of D-glutamic acid-γ-(tert-butyl)ester N-carboxy anhydride in a 1,2-dichloroethane/1,4-dioxane mixture using sodium 4-methyl-2-pyrrolidone as initiator.